This is strange.
Are you familiar with the CLI?
I would suggest SSH/Telnet to the controller, enter "enable" mode (i.e. type enable and enter your secret), then type "conf t".
Try that, and see if you get as far as the configuration prompt. You'll know you're in it when you see it.
Then create a server... example...
aaa authentication-server radius "my-server"
host <IP-ADDRESS-HERE>
key <SECRET_HERE>
!
type exit until back at the enable prompt (denoted with a hash).
Then type "write mem".
Then try again to see if the server exists in the config. You can do a "show run" in the CLI if liked.